You won't catch John Durant in a tie. Shoes are optional, too. He has traded cubicle life for something a little wild: Promoting the diet and lifestyle of our ancestors from the paleolithic era. He's blogging and writing a book about his approach.

"For millions of years, we didn't have an obesity problem because we ate foods that our metabolism was adapted to," Durant says — foods such as root vegetables, tubers, fish and, of course, red meat.

"We were active and lived a healthy lifestyle," he says. Durant is one of many folks following the popular meat-laden paleo diet. He packs his freezer with deer meat and has found lots of places near his home in Manhattan to buy marrow bones and organ meats, as well as paleo-friendly barbecue joints for a meal out.

But modern medicine tells us that too much meat is bad for us, so what's a consumer to do?

During a workout at a CrossFit gym, a gathering spot for lots of paleo-enthusiasts, Durant told me it's no longer a challenge for him to avoid the onslaught of bagels and pizza at every street corner. The paleo approach is to eliminate grains and processed food, which are relatively new to the human diet. And, as a result, Durant says, he no longer gets the spikes and dips in his moods, and he feels better.

But Durant says it's a meat-based diet that was fundamental to early human development. (Check out our tongue-in-cheek Time Traveler's Cookbook: Meat Lover's Edition for more on this.)

My colleague Chris Joyce has reported on how a meat-based diet helped make us smarter.

And paleoanthropologist John Hawks at the University of Wisonsin, Madison, agrees: "We definitely evolved to eat meat."

"When we look at the fossils of early Homo [sapien], we see this immediate increase in the size of the body and also increase in the size of the brain," Hawks explains.

But that was then. Very few cavemen lived long enough to get heart disease or cancer. These are the reasons we're told to limit red meat consumption now.

"It really began in a big way in the Framingham study in the 1950s," says Michael Thun, an epidemiologist with the American Cancer Society.

"It [the study] found a relationship between total cholesterol and heart disease," Thun says. Over the years, there has been debate about whether high cholesterol is a cause or simply a marker of higher heart disease risks. But studies like this one helped raise the red flag about high-cholesterol foods, such as red meat.

Then, the evidence started mounting that people who ate daily servings of red meat increased their risks of developing certain cancers. For colon cancer, studies show that people who eat the most have about double the risk compared with people who eat the least red meat.

"That's been found in lots of studies," says Thun, "so it's pretty well-accepted."

Paleo enthusiast John Durant says he has thought about these studies and has heard the health experts, but he's not worried. He says lots of the people in these big epidemiological studies are sedentary and overweight.

He may be eating more red meat than the experts recommend, but he believes his paleo lifestyle, which includes running barefoot in Central Park, helps keep him thin, active and healthy. And he's not alone — the movement is attracting some medical professionals.

Because there are no studies of people who've been following the paleo diet, Thun says, it's hard to evaluate. "There's just not been enough people eating one kind of paleolithic diet to tell."

As for the rest of us who want to know how much red meat is too much, the best evidence suggests that cutting back to two to three servings a week is a good guide.

With a pinch of skepticism and a dash of fun, The Salt covers food news from the farm to the plate and beyond. You can connect with senior editor and host Maria Godoy via our contact form or directly by email. You can also reach correspondent Allison Aubrey via email.